Electronic device and method for producing an electronic device

ABSTRACT

The invention relates to an electronic device comprising a printed circuit board ( 14 ) and comprising an electronic component ( 16 ) arranged on a first surface ( 15 ) of the printed circuit board ( 14 ). The printed circuit board ( 14 ) has a cutout ( 23 ) extending from a second surface ( 24 ) of the printed circuit board ( 14 ), said second surface being situated opposite the first surface ( 15 ), in the direction of the electronic component ( 16 ). The electronic device comprises a coolant container ( 25 ), which has an opening closed by the second surface ( 24 ) of the printed circuit board ( 14 ). The invention additionally relates to a method for producing such an electronic device.

FIELD OF THE INVENTION

The invention relates to an electronic device having an electroniccomponent arranged on a first surface of a printed circuit board. Theinvention additionally relates to a method for producing such anelectronic device.

BACKGROUND OF THE INVENTION

During the operation of such electronic devices heat is generated. Thisholds true, in particular, if the component is operated with high power,as is the case for a power semiconductor, for example. Printed circuitboards are known which have cooling channels extending in theirinterior, with a cooling liquid flowing through said cooling channelsduring the operation of the printed circuit board, DE 10 2004 062 441B3, DE 20 2010 017 772 U1. The production of such cooling channels inthe interior of the printed circuit board involves a high outlay.

SUMMARY OF THE INVENTION

The invention is based on the object of presenting a printed circuitboard and a method for producing such a printed circuit board in whichthe outlay is reduced.

Departing from the cited prior art, the object is achieved by means ofthe features of the invention as disclosed herein.

Advantageous embodiments are specified herein.

The invention proposes an electronic device which comprises a printedcircuit board and an electronic component arranged on a first surface ofthe printed circuit board. The printed circuit board has a cutout orrecess extending from a second surface of the printed circuit board,said second surface being situated opposite the first surface, in thedirection of the electronic component. The electronic deviceadditionally comprises a coolant container. The coolant container has anopening closed by the second surface of the printed circuit board.

The component can be an active or passive electronic component. Inparticular, the component can be a semiconductor component, for examplein the form of a power semiconductor. A shunt, for example, isappropriate as a passive electronic component.

By virtue of the coolant container having an opening aligned in thedirection of the printed circuit board, a cooling liquid contained inthe coolant container can make direct contact with the printed circuitboard and thereby effectively dissipate heat from the printed circuitboard. The material thickness of the printed circuit board is reduced inthe region of the cutout or recess, such that heat emitted by theelectronic component can readily be transferred into the cooling liquid,without the heat spreading over a large area in the printed circuitboard.

In order to ensure a good heat transfer from the electronic component tothe cooling liquid, the material thickness in the region of the cutoutcan be significantly less than the thickness of the printed circuitboard. By way of example, the material thickness can be less than 50%,preferably less than 30%, more preferably less than 20%, of thethickness of the printed circuit board.

The cutout or recess can have side faces aligned perpendicularly to theplane of the printed circuit board. The side faces can extend as far asan end face that is parallel to the plane of the printed circuit board.The two sides of the printed circuit board are separated from oneanother by the end face. The cutout does not form a perforation of theprinted circuit board. According to one embodiment, the cutout iscuboid. Embodiments in which the side faces of the cutout form an anglewith the plane of the printed circuit board that is different than 90°are also encompassed.

The cutout can be dimensioned such that it overlaps the electroniccomponent in the Z-direction. The Z-direction is aligned perpendicularlyto the plane of the printed circuit board. In other words, if the cutoutis of at least the same size or larger than the electronic component,then an effective heat transfer from the electronic component in thedirection of the cooling liquid is possible.

The opening of the coolant container can be larger than the cutout inthe printed circuit board. The opening can be larger than the cutout forexample by the factor 2, preferably by the factor 5, more preferably bythe factor 10. The coolant container can be arranged such that thecutout lies completely within the opening. The extent of the coolantcontainer in the Z-direction can be greater than the extent of thecutout in the Z-direction. By way of example, the coolant container,relative to the Z-direction, can be larger than the cutout by the factor1.2, preferably by the factor 2, more preferably by the factor 3.

An end face of the coolant container that surrounds the opening can beconnected to the second surface of the printed circuit board. A sealantcan be arranged between the end face of the coolant container and thesurface of the printed circuit board, such that the coolant is preventedfrom emerging at the connection point. By way of example, a screwconnection can be provided for the mechanical securing of the coolantcontainer on the printed circuit board.

The coolant container can have an inlet opening and an outlet opening,such that it is possible to generate a coolant flow through the coolantcontainer. The coolant container can be connected to a cooling systemcomprising a heat exchanger. Pipelines can extend between the outletopening of the coolant container and the heat exchanger and also betweenthe heat exchanger and the inlet opening of the coolant container, suchthat a coolant circuit can be initiated.

The first surface of the printed circuit board can be covered at leastregionally with an electrically conductive layer. The electroniccomponent can be electrically contacted with the conductive layer.

An electrically insulating layer can be arranged between the cutout andthe electronic component. An electrical contact between the coolant andthe electronic component is thus prevented. In order to achieve a goodheat flow between the electronic component and the cooling liquid, theelectrically insulating layer can have a good thermal conductivity.

The invention also encompasses embodiments in which there is anelectrical contact between the coolant and the electronic component.This is possible, in particular, if the connection contact of theelectronic component that is electrically in contact with the coolant isgrounded.

A surface region of the printed circuit board that is arranged withinthe opening of the coolant container can be in direct contact with thecoolant. The surface region can comprise, in particular, the areas ofthe printed circuit board which adjoin the cutout. Said surface regioncan be electrically insulated from the electronic component.

The electrically insulating material used for printed circuit boardsoften does not have good resistance to liquids. In order to protect theelectrically insulating material from the cooling liquid, the surfaceregion of the printed circuit board that is in contact with the coolantcan be covered with a diffusion-impermeable protective layer. Theprotective layer can be a corrosion-resistant metallic coating, inparticular a coating composed of Cu, Ni or Au or a layer sequencecomposed of these materials. The printed circuit board can thuswithstand even aggressive coolants, such as, for example, glycol or anaqueous glycol solution. The space enclosed between the coolantcontainer and the printed circuit board can be completely filled withthe coolant.

The printed circuit board can be a multilayer printed circuit board.This means that the printed circuit board comprises regions in which aplurality of conductive layers and non-conductive layers succeed oneanother alternately in the Z-direction. There may be plated-throughholes between the conductive layers, such that there are electricalconnections between conductive layers in the Z-direction.

Each of the electrically conductive layers can be electrically insulatedfrom the coolant. In particular, a protective layer applied on thesecond surface of the printed circuit board can be electricallyinsulated from the electrically conductive layers.

It is also possible for thermal vias to be formed between the layers. Athermal via denotes a metallic contact between two conductive layerswhich, in the relevant application, is not used for transmittingelectric currents, but rather serves to reduce the thermal contactresistance between the electronic component and the coolant.

The invention additionally relates to a method for producing anelectronic device. In the method, a cutout or recess is produced in aprinted circuit board, said cutout extending from a second surface inthe direction of a first surface situated opposite the second surface,without perforating the printed circuit board. A coolant containerhaving an opening is thus connected to the second surface of the printedcircuit board such that the opening is closed by the printed circuitboard. A cooling liquid is filled into the coolant container.

In a region of the first surface situated opposite the cutout, anelectronic component to be cooled can be connected to the printedcircuit board. The electronic component to be cooled can be for examplean active component or a passive component.

If, when producing the cutout, electrically conductive layers of theprinted circuit board are cut, then an electrically insulating layer canbe applied within the cutout, which electrically insulates the surfaceof the cutout from the electrically conductive layers. Adiffusion-impermeable protective layer can be applied on the secondsurface of the printed circuit board and covers at least that surfaceregion of the printed circuit board which comes into contact with thecoolant.

The method can be developed with further features described inassociation with the electronic device according to the invention. Theelectronic device can be developed with further features described inassociation with the method according to the invention.

BRIEF DESCRIPTION OF THE INVENTION

The invention is described by way of example below on the basis of anadvantageous embodiment with reference to the accompanying drawing, inwhich:

FIG. 1: shows a schematic sectional illustration of an electronic deviceaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

An electronic device shown in FIG. 1 comprises a printed circuit board14 with a semiconductor component 16 arranged on its top side 15 (firstsurface). The semiconductor component 16 is a power semiconductor in theform of a MOSFET, during the operation of which a considerable amount ofheat is emitted. The semiconductor component 16 is electricallycontacted with an electrically conductive layer 17 that partly coversthe top side of the printed circuit board 14.

The electrically conductive layer 17 is applied on a layer 18 of theprinted circuit board 14 which is electrically insulating, but may havea good thermal conductivity. The printed circuit board 14 is constructedin a multilayer fashion, which means that further electricallyconductive layers 19, 20 alternating with insulating layers 21, 22succeed one another below the electrically insulating layer 18. Betweenthe electrically conductive layers 17, 19, 20 there are plated-throughholes 22 that establish an electrical contact between different layersin the Z-direction.

A cutout or recess 23 is formed in the printed circuit board 14, whichcutout is rectangular in cross section and extends from the underside 24(second surface) of the printed circuit board 14 in the direction of thesemiconductor component 16. The cutout 23 is dimensioned such that itsextent in the X-Y-direction substantially corresponds to thesemiconductor component 16. The cutout 23 is arranged such that itoverlaps the semiconductor component 16 in the Z-direction.

A coolant container 25 is connected to the underside 24 of the printedcircuit board 14, said coolant container being open at its upper end.The coolant container 25 is connected to the underside 24 of the printedcircuit board 14 via an end face 26, such that a closed-off space isformed which is enclosed between the coolant container 25 and theprinted circuit board 14. The cutout 23 of the printed circuit board 14is part of this closed-off space. A sealing material 27 is appliedbetween the end face 26 of the coolant container 25 and the printedcircuit board 14, such that no coolant can emerge even at the connectionpoint.

The coolant container 25 is provided with an inlet opening and an outletopening (not illustrated), via which the coolant container 25 isconnected to a cooling system. In the cooling system, the coolant isguided in a closed circuit extending between the coolant container 25and a heat exchanger. In the heat exchanger, heat is emitted to thesurroundings.

The underside of the printed circuit board 14 is covered with aprotective layer 28 in the form of a Cu—Ni/Cu—Ni—Au coating, such thatthere is no contact between the coolant and the electrically insulatinglayers of the printed circuit board. The protective layer 28 iselectrically insulated from the electrically conductive layers 17, 19,20.

In the configuration according to the invention, the semiconductorcomponent 16 is separated from the coolant merely by the electricallyconductive layer 17, the thin insulating layer 18 and the protectivelayer 28. A low thermal contact resistance thus results, such that theheat can readily be transferred from the semiconductor component to thecooling liquid. With the cooling liquid, the heat is transported away inthe cooling system, such that the semiconductor component 16 iseffectively cooled.

1. An electronic device comprising: a printed circuit board; anelectronic component arranged on a first surface of the printed circuitboard; the printed circuit board has a cutout extending from a secondsurface of the printed circuit board, the second surface being situatedopposite the first surface, in the direction of the electroniccomponent; and a coolant container which has an opening closed by thesecond surface of the printed circuit board.
 2. The electronic device asclaimed in claim 1, wherein the material thickness of the printedcircuit board in the region of the cutout is less than 50%, preferablyless than 30%, more preferably less than 20%, with respect to thethickness of the printed circuit board.
 3. The electronic device asclaimed in claim 1, wherein the cutout has side faces alignedperpendicularly to the plane of the printed circuit board.
 4. Theelectronic device as claimed in claim 1, wherein the cutout overlaps theelectronic component in a direction perpendicular to the plane of theprinted circuit board.
 5. The electronic device as claimed in claim 1,wherein the opening of the coolant container is larger than the cutoutof the printed circuit board.
 6. The electronic device as claimed inclaim 1, wherein the cutout is arranged completely within the opening ofthe coolant container.
 7. The electronic device as claimed in claim 1,wherein, relative to a direction perpendicular to the plane of theprinted circuit board, the extent of the coolant container is largerthan the extent of the cutout.
 8. The electronic device as claimed inclaim 1, wherein an electrically insulating layer is arranged betweenthe cutout and the electronic component.
 9. The electronic device asclaimed in claim 1, wherein a surface region of the printed circuitboard that is arranged within the opening of the coolant container iselectrically insulated from the electronic component.
 10. The electronicdevice as claimed in claim 1, wherein a surface region of the printedcircuit board that is in contact with the coolant is covered with adiffusion-impermeable protective layer.
 11. The electronic device asclaimed in claim 10, wherein the protective layer is a coating composedof Cu, Ni or Au or a layer sequence composed of said metals.
 12. Theelectronic device as claimed in claim 1, wherein the printed circuitboard comprises a plurality of electrically conductive layers, which areelectrically connected to one another, and wherein all the electricallyconductive layers are electrically insulated from the coolant.
 13. Amethod for producing an electronic device, wherein a cutout is producedin a printed circuit board, said cutout extending from a second surfaceof the printed circuit board in the direction of a first surfacesituated opposite the second surface, without perforating the printedcircuit board, wherein a coolant container having an opening isconnected to the second surface of the printed circuit board in such away that the opening is closed by the printed circuit board, and whereina cooling liquid is filled into the coolant container.
 14. The method asclaimed in claim 13, wherein, when producing the cutout, an electricallyconductive layer of the printed circuit board is cut, and wherein anelectrically insulating layer is applied within the cutout, such thatthe surface of the cutout is electrically insulated from theelectrically conductive layers.
 15. The method as claimed in claim 13,wherein a diffusion-impermeable protective layer is applied on thesecond surface of the printed circuit board and covers at least thesurface region of the printed circuit board which comes into contactwith the coolant.